From Ashburn (click to change), it will be visible between 21:50 and 04:24. It will become accessible at around 21:50, when it rises 24° above your south-eastern horizon, and then reach its highest point in the sky at 01:09, 43° above your southern horizon. It will become inaccessible at around 04:24 when it sinks to 25° above your south-western horizon.

Neptune opposite the Sun

This optimal positioning occurs when Neptune is almost directly opposite
the Sun in the sky. Since the Sun reaches its greatest distance below the
horizon at midnight, the point opposite to it is highest in the sky at the same
time.

At around the same time that Neptune passes opposition, it also makes
its closest approach to the Earth – termed its perigee –
making it appear at its
brightest and largest.

This happens because when Neptune lies opposite the Sun in the sky, the
solar system is lined up so that Neptune, the Earth and the Sun form a
straight line with the Earth in the middle, on the same side of the Sun as
Neptune.

In practice, however, Neptune orbits much further out in the solar system than the Earth – at an average distance from the Sun of 30.27 times that of the Earth,
and so its angular size does not vary much as it cycles between
opposition and solar conjunction.

On this occasion, Neptune will lie at a distance of
28.94 AU,
and its disk will measure
2.4 arcsec
in diameter, shining at magnitude 7.8. Even at its closest approach
to the Earth, however, it is not possible to distinguish it as more than a
star-like point of light
without the aid of a telescope.

Neptune in coming weeks

Over the weeks following its opposition, Neptune will reach
its highest point in the sky four minutes earlier each night, gradually
receding from the pre-dawn morning sky while remaining visible in the evening
sky for a few months.

A chart of the path of Neptune across the sky in 2017 can be found here, and a chart of its rising and setting times here.

Source

The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.